Method for Producing Fluorinated Compounds and Polymers

ABSTRACT

A fluorinated polymer comprising a unit represented by the following formula (1), a method for producing fluorinated compounds and the fluorinated polymers, and an optical/electrical material or coating material comprising the fluorinated polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. application Ser. No. 10/580,977 filed May 31,2006, which is the U.S. National Phase of PCT/JP2004/017905 filed Nov.25, 2004, based on U.S. Provisional application Ser. No. 60/525,865filed Dec. 1, 2003, and JP 2004-178766 filed Jun. 16, 2004, the entirerespective disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel fluorinated polymers and methodfor producing fluorinated compounds and fluorinated polymers.

2. Description of the Related Art

Fluorinated polymers are useful materials that are used in variousapplications, for example, optical members such as plastic opticalfibers and photoresist materials, or surface modifiers. However, thesynthetic processes of fluorinated polymers are complicated and costly.

A fluorinated polymer is obtained by polymerization of a fluorinatedcompound having a polymerizable unsaturated group. As an example offluorinated polymers, 1,3-dioxolane derivatives and the like aredisclosed in U.S. Pat. No. 3,308,107, U.S. Pat. No. 3,450,716; IzvestiyaA Kademii Nank SSSR, Seriya Khimicheskaya. pp. 392-395, February 1988 byV. S. Yuminov et al. and pp/938-, April 1989 by V. S. Yuminov et al; andthe like.

SUMMARY OF THE INVENTION

The present inventors have developed the following useful and novelfluorinated polymers and synthetic methods. The present invention willbe described below.

A first aspect of the present invention is a fluorinated polymercomprising an unit represented by the following formula (1):

A second aspect of the present invention is the fluorinated polymeraccording the first aspect, wherein the fluorinated polymer is ahomopolymer.

A third aspect of the present invention is the fluorinated polymeraccording the first aspect, wherein the fluorinated polymer isrepresented by the following formula (2),

wherein: in Formula (2), Y¹ to Y⁴ each independently represent ahydrogen atom, fluorine atom, or chlorine atom.

A fourth aspect of the present invention is a method for producingfluorinated compounds, in which a compound represented by the followingformula (4) is produced by reaction of2-chloro-2,2-difluoroethane-1,1-diol and at least one compoundrepresented by the following formula (3):

wherein: in Formula (3), X represents a hydroxy group, a chlorine atom,or bromine atom.

A fifth aspect of the present invention is a method for producingfluorinated compounds, in which a compound represented by the followingformula (4) is produced by reaction of 2-chloro-2,2-difluoroacetaldhydeand ethyleneoxide.

A sixth aspect of the present invention is a method for producingfluorinated polymers, in which a polymer comprising an unit representedby the following formula (1) is produced by polymerization thefluorinated compound represented by the following formula (4) obtainedby the method according to the fourth aspect.

A seventh aspect of the present invention is a method for producingfluorinated polymers, in which a polymer comprising an unit representedby the following formula (1) is produced by polymerization thefluorinated compound represented by the following formula (4) obtainedby the method according to the fifth aspect.

A eighth aspect of the present invention is an optical/electricalmaterial or coating material comprising the fluorinated polymeraccording to the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating a ¹HNMR spectrum and a ¹⁹FNMR spectrum ofa polymer synthesized in Example 2.

FIG. 2 is a graph illustrating an X-ray diffraction pattern of a polymersynthesized in Example 2.

FIG. 3 is a graph illustrating a glass transition temperature of apolymer synthesized in Example 2.

FIG. 4. is a graph illustrating a thermal decomposition of a polymersynthesized in Example 2. A; in nitrogen gas atmosphere, B; in airatmosphere.

DETAILED DESCRIPTION OF THE INVENTION 1. Method for ProducingFluorinated Compounds

The polymer of the present invention is obtained by polymerizing a1,3-dioxolane derivative represented by the following formula (4):

First, the producing process of the fluorine-containing compoundrepresented by the above formula (4) will be described. Here, twoproducing processes according to the present invention will bedescribed.

1-1 First Producing Method

The above fluorine-containing compound which is a 1,3-dioxolanederivative is produced by using 2-chloro-2,2-difluoroethane-1,1-diol anda compound represented by the following formula (3):

wherein X represents a hydroxyl group, chlorine atom or bromine atom,preferably represents a chlorine atom.

A reaction scheme of the above compounds is exemplified below, but isnot limited thereto.

The first producing method of the present invention includes thefollowing two steps, and is a simple and inexpensive method:

(1) the step of conducting de-hydrogen halide while performingdehydration from 2-chloro-2,2-difluoroethane-1,1-diol and at least onecompound represented by the formula (3) by the use of calcium chlorideand potassium carbonate, and

(2) the step of conducting de-hydrogen halide, with a base.

The steps of (1) and (2) will be described hereinafter.

Step (1)

2-Chloro-2,2-difluoroethane-1,1-diol and the compound represented by theformula (3) are preferably allowed to react with each other inequimolecular amounts. The compounds represented by the formula (3) maybe used singly or in combination of two or more kinds of the compounds.However, a single kind of the compound is preferably used. Sodiumcarbonate or the like may be used in place of calcium chloride andpotassium carbonate.

As the reaction is an exothermic reaction, the reaction is preferablycarried out while cooling. Other reaction conditions are notspecifically limited, and a purifying process such as distillation maybe preferably performed prior to the step (2)

Step (2)

The compound obtained by Step (1) is subjected to a de-hydrogen halideprocess. The elimination process of the hydrogen halide is carried outby using a strong base such as potassium hydroxide in an alcohol such asethanol. As the base, potassium t-butoxide or the like may be used.

In the producing process of the present invention, steps other thansteps (1) and (2) may be performed.

1-2 Second Producing Method

2-Chloro-2,2-difluoroacetaldehyde is allowed to react with ethyleneoxide to form 1,3-dioxolane derivative-fluorine-containing compoundrepresented by the above formula (4). The reaction scheme of thesecompounds is shown below, but is not restricted thereto.

The second producing method of the present invention includes thefollowing two steps, and is a simple and inexpensive method:

(1) the step of conducting a catalytic reaction of2-chloro-2,2-difluoro-acetaldehyde and ethylene oxide, and

the step of conducting de-hydrogen halide by use of a base.

The steps (1) and (2) will be described hereinafter.

Step (1)

2-Chloro-2,2-difluoroacetaldehyde and ethylene oxide are preferablyallowed to react with each other in equimolecular amounts.

As a catalyst, NiCl₂, CuCl₂, ZnCl₂ and the like can be used. The amountof the catalyst is approximately in the range of 0.001 to 0.01 mole permole of each compound.

As the reaction is an exothermic reaction, the reaction is preferablycarried out while cooling. Other reaction conditions are notspecifically limited, and a purifying process such as distillation maybe preferably performed prior to the step (2)

Step (2)

The compound obtained by step (1) is subjected to a de-hydrogen halideprocess. The elimination process of the hydrogen halide is carried outby using a strong base such as potassium hydroxide in an alcohol such asethanol. As the base, potassium t-butoxide or the like may be used.

In the producing process of the present invention, steps other thansteps (1) and (2) may be performed.

2. Method of Producing Fluorine-Containing Polymer

1,3-Dioxolane derivative represented by the above formula (4) can beeasily polymerized by using a radical polymerization initiator to form apolymer represented by the following formula (1):

The above 1,3-dioxolane derivative represented by the above formula (4)is a 5-membered cyclic compound and a stable substance. In case of6-membered cyclic ring compound, the compound is apt to open the ringduring polymerization process so that the resultant polymer becomes amixture, resulting in decrease in physical properties such as heatresistance and hydrolysis.

The polymer having the following structure (1) can be produced by aconventional radical polymerization process. As radical polymerizationcatalysts, conventional substances can be used. For example, peroxides,and azo type polymerization initiators such as AIBN(2,2-azobisisobutyronitril) can be used.

When only 1,3-dioxolane derivative represented by the above formula (4)is used as a monomer starting material, a homopolymer is obtained. When1,3-dioxolane derivative represented by the above formula (4) andanother monomer are used in combination, a copolymer of the compoundrepresented by the formula (4) and the other monomer is obtained.Another monomer is not specifically limited, as long as the monomer is acompound having a carbon double bond. Such copolymer includes thepolymer represented by the following formula (2):

wherein Y¹ to Y4 each independently represent a hydrogen atom, afluorine atom or a chlorine atom. Preferably, Y¹ to Y⁴ eachindependently represent a fluorine atom or a chlorine atom.

The ratio of n to m is preferably 1:9 to 5:5, and more preferably 2:8 to3:7.

3. Fluorine-Containing Polymer

The polymer having structure of formula (1) is insoluble in a solventsuch as acetone, DMSO, toluene THF, chloroform and methanol, but solublein fluorination solvent such as hexafluoroisopropanol (HFIP) andchloroform containing a small amount of trifluoroacetic acid.

The polymer having structure of formula (1) has a high melting point,and a high glass transition temperature, and is an extremely thermallystable substance. In particular, a homopolymer having structure offormula (1) is a paracrystal body and has a high melting point, and isan extremely thermally stable substance. Further, the polymer havingstructure of formula (1) is still stable in sulfuric acid and a heatedconcentrated aqueous solution of potassium hydroxide.

It is reported that when 2-methylene-1,3-dioxolane in which all fluorineatoms of the compound represented by the above formula (4) aresubstituted with hydrogen atoms is radical-polymerized, the resultantpolymer is partially ring-opened (W. J. Bailey, Z. Ni. and S. Wu; J.Poly. Sci. Polymer Chem. Ed. 20, 3021 (1982)).

When 2-difluoromethylene-1,3-dioxane which has 6-membered ring isradical-polymerized, the compound is apt to open the ring, andtherefore, the resultant polymer is a copolymer and/or a mixture of avinyl addition polymerized polymer and a ring-opened polymer, so thatthe polymer tends to cause deterioration of physical properties such asacid-resistant, alkali-resistant and heat resistant properties. On theother hand, when the compound represented by the above formula (4) issubjected to a radical polymerization reaction by use of a radicalinitiator, the resultant polymer is only a vinyl addition polymer andring-opened polymer is hardly obtained. If resultant polymer is not amixture, the polymer has a higher melting point and a higher glasstransition temperature. Accordingly, the polymer having the structure ofthe formula (1) is chemically and thermally stable. That is, the polymerhaving the structure of the formula (1) has a high crystallinity, andexcellent heat and photo resistance, and therefore, can be used for aspecial paint and the like.

The copolymer represented by the above formula (2) is soluble influorination solvent such as hexafluoroisopropanol (HFIP) and chloroformcontaining a small amount of trifluoroacetic acid.

In comparison with the homopolymer and the copolymer,tetrafluoroethylene polymer which is a fluorine-containing polymer isslightly soluble in solvent. That is, the homopolymer and the copolymerrepresented by the formula (2) of the present invention has a highadhesiveness with the surface of metal or glass due to its solubility,and is applicable to a new thin layer coating material and insulatingmaterial.

Further, when the surface of the film of the homopolymer and thecopolymer is oxidized with dilute nitric acid or potassium permanganate,the surface can have the following functional groups:

The adhesiveness of the surface can greatly be improved by providingwith such functional groups on the surface.

The homopolymer and the copolymer of the invention can be utilized forbeing cast into films, i.e. to prepare solutions for coating on metal,glass and other subjects. The thin film formed is very stable withrespect to chemicals and heat as well as with respect to light. Thus, itis especially useful as a protective coating material.

Next, the present invention will be explained with reference toExamples, but is not limited thereto.

Example 1 Synthesis of Chlorodifluoroacetaldehyde

Chlorodifluoroacetaldehyde was obtained by reducing methylchlorodifluoroacetate with lithium aluminum hydride.

100 g (0.69 mole) of methylchlorodifluoro acetate was added to 100 ml ofanhydrous ether, and placed in a 1 liter-sized three-neck flask having astirrer, funnel and reflux condenser. The flask was cooled in a dryice/acetone bath. In a separate operation, 7 g (0.18 mole) of lithiumaluminum hydride was added to 150 ml of ether solution, and thusobtained slurry was stirred for 2 hours. After stirring, the ethersolution of lithium aluminum hydride was added dropwise tomethylchlorodifluoro acetate separately prepared over three hours. Afteradding lithium aluminum hydride, 20 ml of 95% by mass of ethanol wasadded to the reaction mixture maintained at −78° C. Thereafter, themixture was brought to room temperature. In order to dissolve thealuminum compound, the resultant reaction mixture was poured into a2-liter-sized beaker accommodated with crashed ice and concentratedhydrochloric acid. The mixture was separated into two phases, and theaqueous phase was extracted with ether. The ether portion was distilledat 95° C. to 100° C. without drying. The obtained distillate was almostchlorodifluoroacetaldehyde hydrate (CClF₂CH(OH)₂). The yield was 75%.

Synthesis of 2-Chlorodifluoromethyl-1,3-Dioxolane

157 g (1.4 mole or less) of CClF₂CH(OH)₂, 197 g (1.5 mole) of2-bromoethanol and 20 g of calcium chloride were placed in a 1liter-sized flask with a condenser. The flask was heated at 90° C. for 7hours and cooled to room temperature. The upper phase was transferred toa 5 liter-sized flask, and 2 liters of acetone and 386 g (2.8 moles) ofpotassium carbonate were added to the flask. The mixture was reacted at50° C. for three days, and a solid was precipitated. The solvent wasremoved by distillation. The product was purified by distillation. Theyield of the product was 88% (195 g) and has a boiling point of 62°C./30 mmHg.

¹HNMR was 5.24 ppm (t, 1H, —CH—), 3.94-4.3 ppm (m, 4H, —OCH₂—). ¹⁹FNMR(ppm) was −70.56 ppm (2F, —CF₂—).

Synthesis of 2-Difluoromethylene-1,3-Dioxolane

50 g (0.31 mole) of 2-chlorodifluoromethyl-1,3-dioxolane and 800 ml ofTHF were placed in a flask placed in an ice bath. 37 g (0.33 mole) ofpotassium t-butoxide was added dropwise to the flask. The reaction wasmonitored by ¹⁹FNMR measurement. The signal at 70.56 ppm attributed to2-chlorodifluoromethyl-1,3-dioxolane decreased, and the signal at−136.75 ppm attributed to >C═CF₂ increased with the passage of time.After 85% or more of hydrogenchloride was removed, the monomer wascollected in a cold trap (−78° C.) by use of THF under reduced pressure.

Since 2-difluoromethylene-1,3-dioxolane, which is a reaction product, isapt to be polymerized by heating, the solution was concentrated byremoving THF under vacuum at 0° C. 22.7 g of the monomer at aconcentration of 0.4M was contained in the THF solution. The yield was60%. The THF solution was used for radical polymerization.

¹HNMR CDCl₃) δ (ppm): 4.36 (s, 4H)

¹⁹FNMR (CDCl₃) δ(ppm): −136.04 (s, —CF₂—)

Polymerization of 2-chlorodifluoromethylene-1,3-dioxolane

A solution containing 40 mmol of the monomer obtained in Example1(2-chlorodifluoromethylene-1,3-dioxolane) and 100 ml of THF, and 65 mgof AIBN (0.4 mmol) were placed in a glass tube, and degassed thereof.Thereafter, argon was charged into the glass tube by a 3-cycle vacuumcooler, and the glass tube was sealed, and heated at 60° C. for one day.The polymer was condensed during polymerization. The condensed productwas added to methanol, and precipitated from hexafluoroisopropanolsolution for purification. The yield of2-chlorodifluoromethyl-1,3-dioxolane polymer was 80% and obtained in anamount of 3.9 g.

Example 2 Synthesis of 2-Chlorodifluoromethyl-1,3-Dioxolane

114.5 g (1.11 mole) of 2-chloro-2,2-difluoroacetaldehyde, 44 g (1 mole)of ethylene oxide and 1.3 g (0.01 mole) of NiCl₂ were placed in a 1liter-sized flask with a condenser. The flask was heated at 90° C. for 7hours and cooled to room temperature. The upper phase was transferred toa 5 liter-sized flask, to which 2 liters of acetone and 386 g (2.8moles) of potassium carbonate were added. The mixture was maintained at50° C. for 3 days, resulting in precipitating a solid. The solvent wasremoved by distillation. The reaction product was purified bydistillation. The yield was 88% (129.4 g), and the boiling point of theproduct was 62° C./30 mm Hg.

¹HNMR was 5.24 ppm (t, 1H, —CH—), 3.94-4.3 ppm (m, 4H, —OCH₂—). ¹⁹FNMR(ppm) was −70.56 ppm (2F, —CF₂—).

Synthesis of 2-Difluoromethylene-1,3-Dioxolane

2-difluoromethylene-1,3-dioxolane was obtained in a similar manner asExample 1 by the use of 2-chlorodifluoromethyl-1,3-dioxolane obtained inthe above.

Polymerization of 2-Difluoromethylene-1,3-Dioxolane

2-difluoromethylene-1,3-dioxolane could be polymerized in a similarmanner as Example 1.

Example 3 Copolymer of 2-difluoromethylene-1,3-dioxolane withtetrafluoroethylene

A 200 ml solution of 1,1,2-trichlorotrifluoroethane containing 6 g of2-difluoromethylene-1,3-dioxolane and 0.02 g of perfluoropropionylperoxide were loaded into 1 L autoclave at liquid nitrogen temperaturefor polymerization, equipped for stirring and opening for the loadingand unloading of the reactants. After the solution was degassed underreduced pressure and the autoclave was refilled with argon, 16 g oftetrafluoroethylene was introduced at liquid nitrogen temperature. Thereactor was gradually brought to room temperature and then heated at40-45° C. for 10 hrs. The unreacted monomer and solvent were removed totraps at −78° C. under reduced pressure. After distillation of thesolvent and the unreacted monomer, the solid product was further heatedunder a vacuum at a temperature of 100° C. for 5 hrs. 22 g of the solidproduct was isolated. TGA showed a weight loss of 2% at 450° C. ¹⁹FNMRanalysis indicated that the composition ratio of the dioxolane andtetrafluoroethylene was 0.5 to 2.0, and the product was dissolved influorinated solvent such as hexafluorobenzene.

Example 4 Copolymer of 2-Difluoromethylene-1,3-Dioxolane withTetrafluoroethylene

A 150 ml solution of 1,1,2-trichlorotrifluoroethane containing 3 g of2-difluoromethylene-1,3-dioxolane and 0.02 g of perfluoro-t-butylperoxide were loaded into a 1 L autoclave at liquid nitrogen temperaturefor polymerization. After the solution was degassed under reducedpressure and the autoclave was refilled with argon, 32 g oftetrafluoroethylene was introduced at liquid nitrogen temperature. Thereaction was carried out as described in Example 3. 29 g of the solidproduct was obtained, and the ratio of the dioxolane andtetrafluoroethylene in the copolymer obtained was found to be 0.5 to 10.

Example 5 Characteristics of 2-Chlorodifluoromethyl-1,3-DioxolanePolymer

The resultant polymer was not dissolved in solvents such as acetone,DMSO, toluene, THF, chloroform and methanol, but was dissolved in afluorination solvent such as hexafluoroisopropanol (HFIP) andtrifluoroacetic acid (TFA).

The intrinsic viscosity (η) of the polymer was 0.38 dL/g in a mixedsolvent of chloroform and trifluoroacetic acid (volume ratio: 9/1) at25° C. ¹HNMR and ¹⁹FNMR spectra of the obtained polymer were measured byBruker AC 300 spectrophotometer. Mixed solvent of chloroform andtrifluoroacetic acid (volume ratio: 9/1) was used as solvent. As aninternal standard, TMS for ¹HNMR measurement, and trichlorofluoromethanefor ¹⁹FNMR measurement were used, respectively. The results of themeasurements are shown in FIG. 1.

The peak attributed to fluorinated vinyl group is not shown in ¹HNMR.The peak at 112.00 ppm is characteristic of a saturated fluorinecompound (—CF₂—) in the main chain. Only one peak in ¹HNMR appeared at4.26 ppm, which was identified as a proton on a dioxolane ring. Theexistence of opened ring products was not confirmed by the IR and NMRmeasurements, and it was found that only vinyl addition reactionoccurred.

As shown in FIG. 2, the X-ray diffraction pattern of the polymer powdershowed that the polymer was a paracrystal body, and the crystallinitythereof was approximately 44%. The melting point of the polymer was 356°C. which was higher than that of polyfluonated ethylene, 327° C.

As shown in FIG. 3, the glass transition temperature of the polymer ofthe present invention was 125° C. The polymer showed a high thermalstability under a nitrogen gas atmosphere as a result of athermogravimetric analysis. As shown in FIG. 4, a thermal decompositionof the polymer was started at 427° C. under a nitrogen gas atmosphere(A) and started at 414° C. under an air atmosphere (B).

A transparent thin polymer film (0.1 mm or less in thickness) wasobtained by casting an HFIP solution containing the polymer on a glasssubstrate or a silicon substrate. The thin film thus prepared was placedon a Metricon model 2010 prism coupler, and the refractive index thereofwas measured. The refractive index of the film was 1.4396 at thewavelength of 632.8 nm, and 1.4372 at the wavelength of 1544 nm,respectively.

The thin film having a thickness of 0.5 mm or less was immersed in eachof 20% by mass of an aqueous sulfuric acid solution, and 30% by mass ofan aqueous sodium hydroxide solution at 60° C. for two days. Thereafter,the films were washed with water and dried. An IR spectrum and massmeasurements were carried out for the dried films, and deterioration ofthe performance of the films was not found.

As described above, the resultant polymer was extremely thermally andchemically stable, and suitable for materials for electrical componentsand optical elements, in particular, most suitable for application forspecial paint use.

Example 6

The copolymer obtained in example 1 was casted on glass plate. Thepolymer coated plate (polymer thickness=0.1-0.3 mm) was treated withHNO3/H2SO4 at 50-60° C. for 5 hrs. After the film was washed thoroughlywith water and dried at 100° C. under vacuum, the surface was examinedby IR measurements. The spectra indicated that —OH and —C═O— groups wereproduced on the surface. The adhesivity of the film toward aluminum andglass was greatly increased.

1. A method for producing fluorinated compounds, comprising producing acompound represented by formula (4) by reacting2-chloro-2,2-difluoroethane-1,1-diol and at least one compoundrepresented by formula (3)

wherein in Formula (3), X represents a hydroxy group, a chlorine atom,or a bromine atom.
 2. A method for producing fluorinated compounds,comprising producing a compound represented by formula (4), by reacting2-chloro-2,2-difluoroacetaldhyde and ethylene oxide.


3. A method for producing fluorinated polymers, comprising producing apolymer represented by formula (1) by polymerizing the fluorinatedcompound represented by formula (4) obtained by the method according toclaim 2.